There are two key criteria that we use to judge the quality of a particular facial expression: clarity and intensity. If a face has high clarity, more than 80-90% of viewers will agree on the emotion it is portraying. Intensity, on the other hand, is a measure of how strong that emotion appears to be. As you might imagine, faces with high intensity generally also have high clarity, and less intense faces are somewhat harder to interpret.

But not necessarily! With certain expressions, like anger, it is possible to have faces with both low intensity and high clarity, allowing an artist or animator to successfully portray a full range of emotional states, from mere irritation to full-on rage like our one-eyed, mythological friend, the Cyclops.

In this blog post, I examine the many stages of anger, as it rises in intensity while maintaining clarity, as determined by user tests, after lots and lots of earlier experiments to “tune up” the pose. Each test had 50 respondents.

In Figure 1, I have drawn the lowest possible level of anger that can still be recognized. The strong action of the frowning eyebrows, combined with slightly widened eyes (more white showing), is interpreted as anger in spite of the neutral mouth. And, I have gotten 86% user agreement on the interpretation of this drawing as "anger."

Figure 2: Getting Mad with angry eyes and compressed mouth.

In Figure 2, this face is identical to the above, with the exception that the mouth has been drawn so as to appear compressed. As you can see, the "anger" score in my user tests bumps up slightly to 92%.

Figure 2 (left) side by side Figure 1, for comparison.

​A little can count for a lot with facial expressions! When Figures 1 and 2, the two slightly angry faces, are compared to each other in further user tests, the simple difference of the compressed mouth makes Figure 2 seem more angry to 75% of the respondents. Note that the eyes also seem angrier in Figure 2, but that is something we imagine – the eyes are identical in both drawings.

​Marching up the intensity ladder, Figure 3 is seen as angrier than the winner of the previous "face off" by almost 80% of respondents. The only difference? Figure 3 has slightly more widened eyes, with white showing above the iris. This is a really clear example of the power of the "Hot Spot" of the eye (see also my previous blog posts on 3/1/2017 and 1/1/2017), where I examine our super-sensitivity to perceiving the intensity of anger by the smallest change of exposed eye whites. Animators beware: current motion capture technology is not sensitive enough to accurately reflect such subtle differences.

Here, two faces with compressed lips are compared, and Figure 4 on the right is seen as angrier by virtually all of my testers. In Figure 4, the chin muscle is much more strongly contracted, and the lower lip is pushed upwards, particularly in the middle. The mouth is also more strongly pulled down at the corners.

​We learn through testing that the mouth is more decisive in anger than the eyes. Here the shouting mouth is perceived as angrier than the other drawings with closed angry mouths by a huge majority of viewers -- regardless of how open the eyes appear.

​The Winner! In Figure 6, the snarling, widened mouth, showing both upper and lower teeth, is anger at its most intense – surprisingly more intense that the shouting mouth of Figure 5. The only difference between these two images is the amount of teeth exposed.

Below, I have created a serial lineup of a progressively angrier face all with high clarity, from least intense to most intense, based on my test results:

Annoyed

Getting Mad

Getting Angrier

Getting More Angry

Shouting Mad

Enraged

Not all expressions have the same ability to be clearly perceived at all different levels of intensity; fear is particularly difficult to portray clearly at lower intensity, like worry. But judging from the number of angry lions, birds, toys, and evil crabs in recent movies, there is plenty of work out there for artists skilled in manipulating the stages of anger. And, speaking of creatures, Harryhausen's Cyclops (shown above) is identical to my "Enraged" face, except the Cyclops has more widely-opened eyes, which make him look even angrier!

Post Script : For the last several years, I’ve worked with an interdisciplinary team at the University of Washington in Seattle, focused on the language of facial expression on stylized – i.e. animated – faces. Our group, FERG (Facial Expression Research Group), includes computer vision scientists, animators, and artists. focused on the language of facial expression on stylized – i.e. animated – faces. Our group, FERG (Facial Expression Research Group), includes computer vision scientists, animators, and artists. ​One of our research goals has been to determine the optimal patterns for the cardinal expressions, the “secret” formula that will make joy, or surprise, or sadness, the most recognizable. And there is no doubt that such patterns exist, because faces which contain the right configuration of features will be recognized by random viewers in exactly the same way, time and time again.

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So many faces. So many ways to express emotions. Faigin examines facial expressions in movie stills, cartoons, fine art, illustrations and photographs and shares his insightful analyses in his monthly blog.

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